1. Field of the Invention
This invention relates generally to a switch assembly and, more particularly, it relates to a switch assembly built with a simple control circuit and an associated thermal-sensitive alloy leaf for cutting off power supply automatically in case of overload so as to ensure safety.
2. Description of the Prior Art
A power switch is a widely used electronic component for ON/OFF control of a power supply, and is highlighted in its structural complexity in consideration of cost, and particularly, of its reliability of safety.
A generic power switch is a manipulative switch. In some districts where electric power lacks stability, unexpected overload may occur occasionally to bring about overheat that could possibly result in public dangers.
For the improvement of a switch assembly, many patents, such as U.S. Pat. No. 5,786,742, 5,223,813, 4,937,548, 4,661,667, 4,931,762, 5,451,729, and 4,709,594 have been disclosed, wherein a bimetal thermal-sensitive element is implemented for cutting off power supply automatically in case of overload.
For example, the U.S. Pat. No. 4,937,548 has disclosed a mechanism including a bimetal piece, a lever controlled by the bimetal piece, and a cam associated with a see-saw member for controlling contact or separation of two conductive plates and for displacing the lever when the bimetal is heated and deformed to thereby remove the support of the cam to cut off the power supply. Whereas, the bimetal is to react to the overload current directly while the conductive plates are separated by indirect interaction through the bimetal, the cam, and the see-saw member in a somewhat abrupt response with possible malfunctions. Hence, there is still some time for the overload current to pass through an electric appliance and destroy it instantaneously. In addition, it requires an extra wire for connection of the conductive plate and the bimetal to complicate the structure.
In the U.S. Pat. No. 5,786,742, deformation of an overheated alloy leaf drives a limit seat to have a switch knob escaped and reset. However, the contact points could probably contact with each other when overloading occurs because the switch knob drives one of the contact points directly. Therefore, there is a need in improving the abrupt response and complicated structure of a switch although the above patents can solve the overload problem in one way or another.
The primary object of this invention is to provide a switch assembly comprising a switch knob, a contact control member, and an alloy leaf for cutting off power supply rapidly to ensure safety in the event of overload.
Another object of this invention is to provide a switch assembly with simple interactive mechanism by means of a protuberance of a switch knob, wherein the protuberance oppresses or release a contact control member directly to enable the latter to in turn oppress or release a resilient member to connect or cut off a power supply.
For more detailed information regarding this invention together with further advantages or features thereof, at least an example of preferred embodiment will be elucidated below with reference to the annexed drawings.